/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Copyright (C) 2023-2025 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.

    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

\*---------------------------------------------------------------------------*/

#include "twoPhaseVoFSolver.H"
#include "fvcSmooth.H"
#include "fvcSurfaceIntegrate.H"
#include "fvcAverage.H"

// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //

void Foam::solvers::twoPhaseVoFSolver::setInterfaceRDeltaT
(
    volScalarField& rDeltaT
)
{
    const dictionary& pimpleDict = pimple.dict();

    const scalar maxCo
    (
        pimpleDict.lookupOrDefault<scalar>("maxCo", 0.9)
    );

    const scalar maxAlphaCo
    (
        pimpleDict.lookupOrDefault<scalar>("maxAlphaCo", 0.2)
    );

    const scalar rDeltaTSmoothingCoeff
    (
        pimpleDict.lookupOrDefault<scalar>("rDeltaTSmoothingCoeff", 0.1)
    );

    const label nAlphaSpreadIter
    (
        pimpleDict.lookupOrDefault<label>("nAlphaSpreadIter", 1)
    );

    const scalar alphaSpreadDiff
    (
        pimpleDict.lookupOrDefault<scalar>("alphaSpreadDiff", 0.2)
    );

    const scalar alphaSpreadMax
    (
        pimpleDict.lookupOrDefault<scalar>("alphaSpreadMax", 0.99)
    );

    const scalar alphaSpreadMin
    (
        pimpleDict.lookupOrDefault<scalar>("alphaSpreadMin", 0.01)
    );

    const label nAlphaSweepIter
    (
        pimpleDict.lookupOrDefault<label>("nAlphaSweepIter", 5)
    );

    if (maxAlphaCo < maxCo)
    {
        // Further limit the reciprocal time-step
        // in the vicinity of the interface

        volScalarField alpha1Bar(fvc::average(alpha1));

        rDeltaT.internalFieldRef() =
            max
            (
                rDeltaT(),
                pos0(alpha1Bar() - alphaSpreadMin)
               *pos0(alphaSpreadMax - alpha1Bar())
               *fvc::surfaceSum(mag(phi))/((2*maxAlphaCo)*mesh.V())
            );
    }

    // Update the boundary values of the reciprocal time-step
    rDeltaT.correctBoundaryConditions();

    Info<< "Flow and interface time scale min/max = "
        << gMin(1/rDeltaT.primitiveField())
        << ", " << gMax(1/rDeltaT.primitiveField()) << endl;

    if (rDeltaTSmoothingCoeff < 1.0)
    {
        fvc::smooth(rDeltaT, rDeltaTSmoothingCoeff);
    }

    if (nAlphaSpreadIter > 0)
    {
        fvc::spread
        (
            rDeltaT,
            alpha1,
            nAlphaSpreadIter,
            alphaSpreadDiff,
            alphaSpreadMax,
            alphaSpreadMin
        );
    }

    if (nAlphaSweepIter > 0)
    {
        fvc::sweep(rDeltaT, alpha1, nAlphaSweepIter, alphaSpreadDiff);
    }

    Info<< "Smoothed flow time scale min/max = "
        << gMin(1/rDeltaT.primitiveField())
        << ", " << gMax(1/rDeltaT.primitiveField()) << endl;
}


// ************************************************************************* //
